Crimpable composite filament



June 12, 1962 Filed March 16. 1959 2 Sheets-Sheet 1 INVENTOR GORDON MARS MOULDS ATTORNEY June 12 1962 G. M. MouLbs 3,038,239

CRIMPABLE COMPOSITE FILAMENT Filed March 16. 1959 2 Sheets-Sheet 2 INVENTOR GORDON MARS MOULDS A ORNEY United States Patent 3,038,239 CABLE QUMIPQSITE FILAMENT Gordon M. Moulds, Waynesboro, Va., assignor to E. I. du Pont de Nemours and Company, Wilmington, DeL, a corporation of Delaware Filed Mar. 16, 1959, Ser. No. 799,617 12 Claims. (Cl. 28-82) This invention relates to synthetic textile fibers and particularly to improved crimped composite filaments.

In the course of the development of the synthetic textile fiber industry, much effort has'been expended towards-the production of fibers which retain the wellknown advantages of synthetic fibers such as ease-of-case, durability,

and improved mechanical properties, but which, at the same time, possess the properties required to obtain fabrics of outstanding aesthetic appeal-such, for example, as that which characterizes wool fabrics. Wool fabrics have good bulk and cover, obtainable at a relatively low finishing shrinkage which is quite desirable from aneconomic standpoint. In addition, wool fabrics have excellent elastic properties such as stretchability, compressional resilience. and liveliness, and display a pleasing surface handle. Finally, the surface of wool fabrics is renewable; evenafter such severe deformations as crushing or glazing, a

ting, steaming, or mere recovery in humid air.

Although different proposals of the prior art have attained one or more characteristics of wool fabrics, in no instance have such synthetic materials been properly considered as being wool-like in other than superficial appearance.

It has been proposed to improve fabric properties by imparting to the synthetic fibers a spiral crimp. Fibers of this type have been prepared by use of special spinning new surface can easily be obtained, for example by wetconditions or after-treatments which bring about diiferential physical proverties over the cross section of single component filaments, or by spinning together two or more materials to form a composite filament, ie, one which contains the components in an eccentric relationship over the cross section of the filaments. If the two components of a composite filament possess substantially different shrinkage, a crimp is caused by the. dilferential shrinkage of the spun and drawn components.

More recently, it has been proposed to produce crimped composite filaments of synthetically formed polymers having the capacity of changing the amount of crimp upon being exposed to the effect .of..a .swelling agent and upon reverting to the original crimp upon removal of the swelling agent. This characteristic is, for convenience, referred to as reversible crimp; generally speaking, this characteristic of the filaments is observed by the squirming of the filaments upon both application and removing of the swelling agent. The value of this crimp reversibility is evidenced by the ability of the filaments in yarns,

when embodied in a fabric, to squirm or twist around in the fabric under the influence of a swelling agent such as water (and also on removal of the swelling agent), but, nevertheless, to regain the original crimp in the fabric with removal of the swelling agent, as by drying. Fabrics containing these filaments acquire a high degree of fullness or covering power and bulk as a result of the swelling treatment and retain or even increase this fullness after being subjected to such treatments repeatedly. Since the finishing shrinkage is low, the yarns of fabrics containing such filaments have a relatively open structure so that the fabrics exhibit unusual elastic properties.

This invention is concerned with a class of improved composite filaments. These filaments have at least two hydrophobic polymers in eccentric relationship. By the term hydrophobic polymers is meant those polymers having the characteristic of absorbing not more than about 3,38,239 Patented June 12, I962 5% of their dry Weight of water when filaments or yarns of such polymers are exposed to an atmosphere of 65% relative humidity at 70 F.

It is an object of this invention to produce a new and novel crimped composite filament having a crimp repreferably greater than 10%, in an amount such that the fraction of the wate'r absorbent polymer in the blend times 7 its water absorption is at least'LO. That is, if the polymer to be added has awa'ter absorption of 20%, it must be presentto the extent of atleast' l/20 of the blended component. The blended component should preferably contain no morethan about 50% by weight of water absorbent polymer. The composite filament must be crimpable from the straight state upon shrinking. The presence of the water absorbent polymer imparts or increases crimp reversibility upon treatment with and subsequent removal of water. It will be obvious that a small amount of the water-sensitive polymer can be present in one component and a correspondingly larger amount in the other component for purposes of dyeability, etc. without losing the advantages of the invention.

By the expression synthetic polymer is meant a polymer that has been man-made from relatively low molecular weight compounds (monomers) by addition or condensation polymerization methods.

The new improved filaments of this invention may be obtained by spinning together two or more selected synthetic polymeric materials, at least one of which isfiberforming, in such a way that the materials form over the cross sectionof the single composite filament two or more distinct zones which extend through the entire length of the filament in eccentric fashion, whereby only one, or

alternatively, part of or all the components form the surface of the single composite filament. (For convenience, the following discussion will refer to two-component filaments although the filaments may, if desired, have more than two components.) A spinneret apparatus suitable for this purpose is described below.,

Referring to the drawings:

FIGURE 1 is a central cross-sectional elevation of a spinneret assembly which can be used to make the composite filaments of this invention; 7

FIGURE '2 is a transverse cross-sectional plan view of the apparatus of FIGURE 1 taken at 2?. thereof and showing details of the top of the back plate;

FIGURE 3 is a transverse cross-sectional plan view taken at 3-3 of FIGURE I showing details of the bottom of the back plate;

FIGURE 1A is an enlarged portion taken from FIGURE 1 to show details of the spinneret atthe spinning orifice; and r FIGURES 4, 5, and 6 show greatly magnified cross sections, i.e., sections perpendicular to the filament axis, of typical filaments of this invention produced by dry spinning. In these drawings one component is shaded to SllOWV the separation between components.

With reference to FIGURE 1, the bottom spinneret plate 2 which contains a circle of o'rifices 3 is held in place against back plate 1 by retaining rings 12 and 14 and by bolt 13. Afine-mesh screen 4 e.g., 200 mesh per inch, is pressed into position between, and serves as a spacer between spinneret plate 2 and back plate 1. Back plate 1 contains two annular chambers 8 and 9 which are connected to suitable piping and filtration apparatus (not shown) to receive different spinning compositions. Lead holes 11 go from annular chamber 9 to annular space 7. Lead holes 10 lead from annular chamber 8 to annular space 6. Annular spaces 6 and 7 are separated by wall which is disposed above orifices 3 and spaced from spinneret plate 2 by screen 4 to permit free and contiguous passage of the spinning fluids from annular spaces 6 and 7 through orifices 3, the mesh of screen 4 being fine enough to permit spinning fluid passage through orifices 3, as shown in detail in FIGURE 1A.

In FIGURE 2 are shown four lead holes and four lead holes 11 equally spaced within the concentric chambers 8 and 9, respectively.

In FIGURE 3 are shown the concentric inner and outer annular spaces 6 and 7 and the fine-mesh screen 4 partially in section.

Operation of the described apparatus in the practice of this invention is readily understood. Separate spinning materials are supplied to the inner annular chamber 9 and outer annular chamber 8, respectively, of the back plate; the former fiows from chamber 9 through the lead holes 11 into the inner annular space 7 and thence through screen 4 and orifice 3 to forma part of a composite filament, while the latter passes through the lead hole 10 to the outer annular space 6 and thence through screen 4 and the outer side of the orifice 3 to form the other part of the composite filament.

The water absorption of a polymer is determined by the following test:

A one gram polymer sample that will pass a 40-mesh screen is placed in a room at 75 F., 65% relative humidity for 70 hours. The sample is weighed (Weight moist), dried at 110 C. for 3 hours and reweighed (weight dry) polymer weight, moist-polymer weight, dry l00 The equilibrium crimp reversibility of the filaments of this invention are determined by the following test:

A single filament is separated from the single end or tow of drawn, unrelaxed fibers. A three-inch length of the filament is attached to opposite sides of a rectangular copper wire frame with 30% slack between the ends. The frame and filament is then boiled off for 15 minutes to develop the crimp. The crimped filament is then transferred to a special viewing holder by taping or gluing the ends so that about 10% slack is present and the filament length between the clamped ends is approximately 2.5 inches. The filament and viewing holder is then mounted vertically in a stoppered test tube containing desiccant. The tube is stored vertically overnight (l824 hours) at 70 C. Following this conditioning period to dry the filament the tube is then brought to room temperature (approximately C.). After allowing minutes for cooling, the total number of crimps in the filament between the fixed ends are counted. In counting, any crimp reversal points present are ignored. The desiccant is then removed from the glass tube, the tube filled with water and stored vertically at 70 C. for 6 hours. The number of crimps in the wet fiber are counted as above. The cycles are repeated as required to obtain reproducible results.

The equilibrium crimp reversibility (ECR) is expressed as the relative change in crimps from dry to wet as calculated by:

No. of crimps (25dry) No. of crimps (70 wet) X100 ERC N o. of erimps (25 dry) was accomplished by a pretwisting of the filament (prior to exposure to the crimping medium) to the same degree as the crimp frequency found by examination of similar filaments crimped without pretwisting. For crimp reversal measurements, the pretwisted filament was crimped free of tension by immersion in boiling water or other suitable shrinking media. The crimped filament was then suspended in a tube and kept from floating or bending by a small weight (1 milligram) attached to the lower (free) end and insufficient to remove crimp, the weight being pointer shaped to permit measuring and counting rotations of the filament during crimping and uncrimping. The filament was treated successively to 5 cycles each consisting of a 5-minute exposure to 25 C. water followed by a 10-minute drying period in 25 C. moving air. Th revolutions of the pointer (which are equivalent to the crimp changes) for the drying and wetting cycle, were averaged for the 5 cycles and expressed as turns per inch (t.p.i.) of crimped dry filament and are referred to hereinafter as crimp reversibility. The same test was carried out at C. Values from at least three filaments tested as above were averaged to obtain the crimp reversibility of a fiber. The crimp reversibility values were corrected to the 10 crimp per inch level, assuming the crimp reversibility is directly proportional to the crimp frequency.

Another property of the filaments of this invention that is of great importance is their ability to recover from compaction. The following test is used to measure this property.

Crimped fibers were cut in 2-inch lengths, hand carded and made into pellets weighing 0.20 gram. The pellets were placed into a cylinder (0.5 inch diameter hole), heated to 85 C., 1 ml. of water added and compressed under a freely sliding piston that exerted 3.5 p.s.i. for two minutes. The height of the pellet under compression was measured. The compressed pellets were removed from the cylinder and: (1) allowed to recover in dry air for 24 hours and then (2) exposed to steam at atmospheric pressure for 1 minute. The heights of the recovered pellets were measured after treatment 2 and the recovery from compaction calculated:

(height of recovered pellet-compressed height of pellet) X ecovery compressed hei 0f D911ct The expression intrinsic viscosity with the symbol n as used herein signifies the value of 1n(n) at the ordinate axis intercept (i.e., when c equals 0) in a graph of EXAMPLE I (A) A 23% solution of polyacrylonitrile (the homopolymer) of n 2.0 and having a water absorption of 0.9% was prepared in N,N-dimethylformamide (DMF) and constitutes the hydrophobic polymer component. A mixture of 90% polyacrylonitrile of n 2.0, and 10% poly-N-vinylpyrrolidone (water soluble) of n 2.0, and having a water absorption of 20.4% was made and dissolved in DMF to form a 23% solution that was clear. The two polymers were compatible and the mixture had a water absorption of 3.8%. The above two clear spinning solutions were extruded at C. simultaneously from a spinneret similar to that described above having 60 orifices of 0.007 inch indiameter. The solutions were fed to the spinneret so that the polyacrylonitrile component in each filament faced the cell wall. Thecomposite filaments were extruded down into a spinning cell 9 inches in diameter by 19 feet long with a concurrent flow of a mixture of carbon dioxide and nitrogen that was at a temperature of 320 C. as it entered the cell around the spinneret, the walls of the spinning cell being maintained at 170 C. and the yarn was wound up at 200 yards per minute. The 600 denier as-spun yarn was drawn to 4.5 times its original length (i.e., 4.5x) in water at 95-98 C. which simultaneously extracted the residual DMF in the yarn. The yarn upon boiling in water developed 14.2 crimps per inch of extended length and had a denier per filament of 3.3. The yarn had an equilibrium crimp reversibility (ECR) of 20.8% and a crimp reversibility of 0.46 and 1.09 t.p.i. at 25 C. and 90 C. respectively. The crimped fiber displayed 321% recovery from compression upon steaming.

(B) A copolymer of n 2.0 containing 90% acrylonitrile and N-vinylpyrrolidone by analysis with a water absorption of 1.3 was made by conventional practices. A 23% solution of this copolymer in DMF and a 23% solution of polyacrylonitrile, n 2.0, were simultaneously spun under the same conditions as above. After drawing as above, the composite filaments (relaxed by boiling) had an equilibrium crimp reversibility of only 7.8% and a crimp reversibility of 0.08 t.p.i. at 25 C. The recovery from compression by steaming Was 127%.

It was surprising that the use of a mixture of poly-N- vinylpyrrolidone and polyacrylonitrile gavea product superior to that obtained when a copolymer of the same composition was used.

EXAMPLE II A 23% solution in DMF of a copolymer having a water absorption of 1.3% and composed of acrylonitrile and styrene sulfonic acid in a ratio of 98/ 2% by Weight was prepared and constitutes the hydrophobic polymer component. The copolymer had an n of 2.0. A 90/ 10 mixture of this copolymer and poly-N-vinylpyrrolidone of n 2.0 was dissolved in DMF to form -a 23% solution that was clear. The two solutions were simultaneously extruded and stretched using the equipment and procedure of Example I so that the pure copolymer component faced the outside of the spinning cell. After boiling in water, the relaxed yarn had 16.8 crimps per inch and a denier per filament of 3.5. The yarn had a crimp reversibility of 0.51 and 0.67 t.p.i. at 25 and 90 C. respectively.

ECR values of 10%, and 29% relative to a fixed dry state at C. were obtained for the wet state at 45, 70, and 90 C. respectively.

Single component filaments prepared from copolymer alone and the polymer mixture alone were spun and treated as above. The two filaments displayed reversible length changes of 2.1 and 4.4% between 25 C. dry and 70 C. wet for the copolymer and blend respectively. The crimped yarn displayed a recovery of 251% from compression upon steaming.

EXAMPLE III (A) A compatible mixture of 90% polyacrylonitrile of n 2.0, and 10% poly-N-vinyl methylformamide of n 2.0 was dissolved in DMF to form a 22% solution. The poly-N-vinyl methylformamide is water soluble and has a waterabsorption of 19.8%. This clear solution and a 22% solution of polyacrylonitrile n 2.0 in DMF were simultaneously-extruded at 110 C. and composite filaments spun and drawn 4.5 X as in Example I. The yarn developed 27.5 crimps per inch of extended length upon boiling in water and had a denier per filament of 3.3. The yarn had an ECR of 20.1% and a crimp reversibility of 0.39 and 1.18 t.p.i. at 25 C. and 90 C. respectively.

(B) The mixture of polymers in Part A was replaced with a copolymer of acrylonitrile and N-vinyl methylformamide 90/10% by-composition having 'an n of 2.0

'6 and a water absorption of 1.4% and composite fibers made using the same equipment and technique. After boiling in water, the yarn had a denier per filament of 2.9 and displayed an equilibrium crimp reversibility of only 6.9% and a crimp reversibility of 0.06 t.p.i. at 25 C.

EXAMPLE IV I The poly-N-vinylpyrrolidone in the mixture in Example II was replaced with poly-N-vinyl methylform amide to afford a compatible mixture and composite filaments spun and drawn as in Example II. The composite filaments after boiling had 19.3 crimps per inch and had an equilibrium crimp reversibility of 15.7%. The crimp reversibility was 0.19 and 0.97 t.p.i. at 25 C. and 90 C. respectively for the 4.2 denier per filament yarn.

EXAMPLE V A 29% solution in DMF of a copolymer composed of 94% acrylonitrile and 6% methyl acrylate by weight was prepared. This copolymer has a water absorption of 1.9 and an n of 1.5. A mixture of of the above polymer and 20% of zein (water insoluble containing 95% minimum protein-Argo Brand made by Corn Products Refining Co. with a water absorption of 6.4%) was dissolved in DMF to give a 29% solution that was slightly turbid. The two solutions were simultaneously extruded using the equipment and method of Example I and the composite filaments drawn as in Example I. After boiling in water, the yarn had 10.0 crimps per inch, an equilibrium crimp reversiblity of 17.8% and displayed a crimp reversibility at C. of 0.87 t.p.i. for the 3.5 d.p.f. filaments. The fibers displayed 350% recovery fromcompression.

EXAMPLE VI Using the technique of Example I two component sideby-side filaments were prepared using polyacrylonitrile for side 1 and a mixture of poly-acrylonitrile and poly- N-vinylpyrrolidone (PNVP) 'for side 2. After the fibers have been drawn 4.5 X in baths of water -98" C. and boiled off, the yarn was cut into staple length and dyed with a lvat dye, Colour Index 59825. The dye bath consisted of the following:

Water liter 3 Sodium chloride grams 60 Sodium hydroxide do 3 Sodium hydrosulfite do 3 Dye--C.I. 59825 do 6 One gram of the staple prepared as above was immersed in the dyepot at the boil for a period of one minute. The sample was then removed and rinsed in a room temperature reducing bath containing one gram per liter each of sodium hydroxide and sodium hydrosulfite. The sample was then rinsed in cold water and then oxidized for one minute in a solution containing 4 grams per liter of 30% hydrogen peroxide and 4 grams per liter of glacial acetic acid. After the oxidation the sample was thoroughly rinsed in water, dried and the reflectance value determined. The results of various combinations are shown in Table 1.

The amount of dye on a fiber or the depth of color are approximately proportional to the K/S value which is a measure of the light reflected froma sample. The larger the K/S value, the deeper the shade. Values around 30 are rather deep shades with values of being almost .the color of the concentrated dyestuff. For comparison the .K/S values for cotton and an acrylonitrile/methyl acrylate 94/6 fiber are 10.73 and 0.51 respectively with the same dye and method. For this green dye the reflectance through a red filter was measured.

Item'C represents a preferred specie of this invention due to its high level ofvat dyeability which allows'union dyeing of blends of this fiber and cotton and the high level of crimp obtained.

The poly-N-vinylpyrrolidone in Example IA is replaced with poly-N,N-dimethyl acrylamide of n 2.0 and composite filaments having a reversible crimp after drawing and boiling are prepared.

It is surprising that although the polydimethyl acrylamide is water-soluble it is not extracted from a fiber made from the above mixture.

EXAMPLE VIII A wholly aromatic polyamide is prepared by condensing a cold mixture of m-phenylene diamine in N,N'-dimethylacetamide with isophthaloyl chloride. A molar quantity of calcium hydroxide is added to the reaction product to neutralize the hydrochloric acid formed as a by-product. The solution containing 18.1% of a polyarnide of inherent viscosity 1.62 (as measured in dimethylacetarnide) and 4.62% CaCl is used as one spinning solution.

To 500 grams of the above solution is added 13.5 grams (15% of the total polymer weight) of poly-N-vinylpyrrolidone which dissolves to form a compatible solution.

The above two solutions are simultaneously extruded at 130 C. through a one-hole spinneret to form a sideby-side filament of both polymer components into a spinning cell heated to 250 C. and the filament wound up at 200 y.-p.m. The as-spun filament is drawn 4 in atmospheric steam and boiled in water to develop the helical crimp. Following the crimp development the filament is immersed in a 75% aqueous solution of formic acid for minutes at 95 C. washed and dried. The dried filament of 4.5 denier has 12.9 crimps per inch of extended length, has a crimp index of 10.7 and an ECR of 17.4%. This polyamide polymer alone is a hydrophobic polymer.

Filaments have been produced in the above examples which consist of about equal parts of the two components or a relatively higher amount of one component and a correspondingly lower amount of the other component. Good results can usually be obtained with composite filaments containing at least 20% by weight of one component and 80% by weight of the polymer blend up to a ratio of 50% by weight of both components.

Polymers suitable for use as a component of the yarns in this invention may be found among all types of synthetic, polymeric, fiber-forming materials. Condensation polymers such as polyesters, polyamides, or polyester amides as described in U.S. Patents 2,071,250; 2,071,253; 2,130,523; 2,130,948; 2,190,770; 2,465,319, as well as polyurethanes as in U.S. Patent 2,731,446 and polyureas are satisfactory. Addition type polymers such as polyhydrocarbons, polyethers and those made from ethylenically unsaturated monomers such as acrylonitrile, vinyl chloride, vinylidene chloride, vinyl acetate and their copolymers with each other and other copolymerizable monomers may be used.

Polymers containing 80% or more combined acrylonitrile are especially preferred due to their resistance to chemical reagents, ultra-violet light degradation and outstanding physical properties. Numerous monomers including ethylenically unsaturated sulfonic acids as the methallyl sulfonic acids and others as disclosed in U.S.

8 Patents 2,527,300 and 2,601,256 can be copolymerized with acrylonitrile as disclosed in Jacobson U.S. 2,436,926 and in Arnold U.S. 2,456,360 to produce Copolymers useful herein.

The water-sensitive polymer used for blending may be a natural or synthetic polymer or copolymer. Preferably it is compatible with the synthetic polymer used in order to produce lustrous, heat-stable, uniform-dyeing filaments.

Compatibility is readily determined by casting a film of the polymeric blend in question by any suitable method as by melt, dry or wet casting from a solution or from a plasticized melt. A clear film after removal of the solvent (if used) is evidence of compatibility. Preferably the film should remain clear after drawing and relaxing.

In the preferred embodiment of this invention polymers containing or more combined acrylonitrile are used and the water-sensitive polymer should preferably be compatible therewith. The following structural criteria may be used to select a suitable water-sensitive polymer:

(1) The ratio of the number of carbon atoms to the polar group (such as should be less than or equal to 5:1.

(2) The polar group should have a dipole moment of greater than 3.5 Debye.

(3) There should be no hydrogen bonding within the polymer. For a discussion of hydrogen bonding in polymers see Nature of The Chemical Bon by L. Pauling published by University Press of Cornell University, New York.

Some typical values (as measured on the monomer) of polymers useful in this invention are shown below.

Carbon Monomer atom/ Dipole Hydrogen polar moment bonding group N vinylpyrrolidone 4:1 3. 7 no. N-vlnylmethyll'ormamide 3:1 3. 6 no. N,N-dimethylacrylamide 4:1 3. 7 no. bls(ethyl)vinyl phosphonate 6: 3 3. 5 no.

wherein x is a cardinal number not greater than 1; R and R are hydrogen or a lower alkyl group; R and R directly joined complete a five or six membercd ring. Copolymers with the required Water absorption may be used as the water-sensitive blending polymer. Although many types of comonomers may be used with the watersensitive monomer, acrylonitrile is preferably used. In addition to Copolymers containing from 5-50% of acrylonitrile with the previously discussed monomers, the Water-sensitive graft copolymers containing N-acrylyl and N-methacrylyl substituted nitrogen heterocyclic com- 9 pounds as discussed in Us. Patent 2,798,061 may be used.

Although the process of this invention has been illustrated by dry spinning it will be obvious to one skilled in the art that other means of spinning can be used as melt, plasticized melt and wet spinning.

The two polymeric components should be selected so that they have a difference in shrinkage of at least 1% and a difference in reversible length change of more than 0.4% (as determined on single component filaments measured at 25 C. dry and 70 C. wet).

Although this invention has been illustrated by the use of side-by-side structures, a structure which has a core completely and eccentrically surrounded by a sheath is applicable. Such filaments are conveniently spun using a spinneret similar to that shown in copending application 519,031, filed on June 30, 1955, to J. Kilian.

Composite filaments prepared for use in accordance with the present invention may be subjected to a drawing (permanent stretching) operation in order to impart to the filaments the desired physical properties as tenacity, elongation and initial modulus. Although drawing "may effect shrinkability and the reversible length change of a filament, crimped filaments with a reversible crimp have been made from dry-spun filaments Without a drawing treatment. The conditions applied to drawing the spun multi-component filaments may vary in wide limits. The drawing characteristics of the components can readily be determined from those of mono-component filaments of each of the component polymers of the composite filaments. The drawing can be accomplished in accordance with known principles applicable to the particular polymers of the composite filaments and, in general, the composite filaments are drawn at least 50% (i.e., to 150% of original undrawn length) and preferably about 28 times the original lengths. The extent of drawing will, of course, also depend somewhat upon the nature of the particular polymers used in the composite filaments and upon the type of eccentric relationship between those polymers in the composite filament.

In considering the extent of drawing, one should take into consideration the amount of draw which may be effected during the spinning of the filaments, and, in fact, the desired amount of drawing may be effected during spinning rather than as a separate drawing step following the windup of the filaments from the spinning operation.

The shrinking of the composite filaments in order to efiect crimping, may be carried out by the use of any suitable known shrinking agent. Shrinking will ordinarily be carried out by the use of hot aqueous media such as hot or boiling water, steam, or hot highly humid atmosphere, or by the use of hot air or other hot gaseous or liquid media chemically inert to the polymers of the composite filaments. The shrinking temperature is generally in the neighborhood of 100 C. but may be higher or lower, e.g., 50 C. up to about 150 C. or even up to a temperature not exceeding the melting point of the lowest melting polymeric component of the fiber.

The invention is particularly directed to filaments and yarns (i.e., bundles of filaments) having deniers of the magnitude used in textiles. It is preferred that the filaments of this invention have a denier of 1 to (inclusive) and that the yarns of this invention have a denier of 30 to 8,000 (inclusive).

The filaments of this invention are of great utility in all types of textile applications. The crimp reversibility of these filaments enables fabrics containing such filaments to have a high degree of fullness or covering power with unusual and pleasing handles. The sensitivity of the crimp reversibility to difference in temperatures enables T0 the extent of working of filaments in a fabric (or the squirming) to be readily controlled to obtain the end result desired.

The filaments or" this invention also have a great advantage in that many of them are readily dyed with vat dyes so that, for example, union dyeing can be made of blends of these filaments with, for example, cotton and techniques such as pad steam dyeing of vat dyes can be easily used.

What is claimed is:

1. A composite filament crimpable from a straight state upon relaxation by shrinking comprised of at least two synthetic hydrophobic polymeric components, said components being eccentrically disposed towards each other in distinct zones with adjoining surfaces being in intimate adhering contact with each other, each of said components extending throughout the length of said filament, one of said components having a shrinkability greater than any of said other components, and one of said components having admixed therein an amount up to about 50% of its weight of a synthetic polymer having a water absorpticn of at least 6% and having a reversible length change after shrinkage evidenced by an increase in length greater than any of said other components when treated with a swelling agent with said component substantially returning to its original length upon removal of said swelling agent, said filament assuming a crimped stated upon relaxation by shrinking and exhibiting crimp reversibility characterized by squirming of said filament upon treatment with and upon removal of said swelling agent after said shrinking.

2. A composite filament of claim 1 wherein each of said components is comprised of an acrylonitrile polymer having at least combined acrylonitrile.

3. A composite filament of claim 1 wherein each of said components is comprised of a polyamide.

4. The filament of claim 1 wherein the water absorbing polymer is present in an amount such that its water absorption times the fraction it comprises of the mixed polymer component is at least 1.0.

5. The filament of claim 4 wherein the water absorbing polymer is poly-N-vinylmethylformamide.

6. The filament of claim 4 wherein the Water absorbing polymer is poly-N-vinylpyrrolidone.

7. The filament of claim 4 wherein the Water absorbing polymer is zein.

8. The filament of claim 2 wherein the water absorbing polymer is present in an amount such that its water absorption times the fraction it comprises of the mixed polymer component is at least 1.0.

9. The filament of claim 2 wherein the water absorbing polymer is poly-N-vinylmethylformamide.

10. The filament of claim 2 wherein the water absorbing polymer is poly-N-vinylpyrrolidone.

11. The filament of claim 2 wherein the water absorbing polymer is Zein.

12. The filament of claim 3 wherein the Water absorbing polymer is poly-N-vinylpyrrolidone.

References Cited in the file of this patent UNITED STATES PATENTS 2,428,046 Sisson et al. Sept. 30, 1947 2,439,815 Sisson Apr. 20, 1948 2,509,857 Borcherdt et al. May 30, 1950 2,882,253 Letferdink et al Apr. 14, 1959 FOREIGN PATENTS 514,638 Great Britain Nov. 14, 1939 760,179 Great Britain Oct. 31, 1956 

1. A COMPOSITE FILAMENT CRIMPABLE FROM A STRAIGHT STATE UPON RELAXATION BY SHRINKING COMPRISED OF AT LEAST TWO SYNTHETIC HYDROPHOBIC POLYMERIC COMPONENTS, SAID COMPONENTS BEING ECCENTRICALLY DISPOSED TOWARDS EACH OTHER IN DISTINCT ZONES WITH ADJOINING SURFACES BEING IN INTIMATE ADHERING CONTACT WITH EACH OTHER, EACH OF SAID COMPONENTS EXTENDING THROUGHOUT THE LENGTH OF SAID FILAMENT, ONE OF SAID COMPONENTS HAVING A SHRINKABILITY GREATER THAN ANY OF SAID OTHER COMPONENTS, AND ONE OF SAID COMPONENTS HAVING ADMIXED THEREIN AN AMOUNT UP TO ABOUT 50% OF ITS WEIGHT OF A SYNTHETIC POLYMER HAVING A WATER ABSORPTION OF AT LEAST 6% AND HAVING A REVERSIBLE LENGTH CHANGE AFTER SHRINKAGE EVIDENCED BY AN INCREASE IN LENGTH GREATER THAN ANY OF SAID OTHER COMPONENTS WHEN TREATED WITH A SWELLING AGENT WITH SAID COMPONENT SUBSTANTIALLY RETURNING TO ITS ORIGINAL LENGTH UPON REMOVAL OF SAID SWELLING AGENT, SAID FILAMENT ASSUMING A CRIMPED STATED UPON RELAXATION BY SHRINKING AND EXHIBITING CRIMP REVERSIBILITY CHARACTERIZED BY SQUIRMING OF SAID FILAMENT UPON TREATMENT WITH AND UPON REMOVAL OF SAID SWELLING AGENT AFTER SAID SHRINKING. 